Script works inconsistently
Non blender internal textures

There may be some textures in blend that don't have the use_interpolation property.  For example switch to cycles and add a new brush texture.  bpy.data.textures["Texture"] the newly added one, doesn't.

Check whether the texture has the attribute with hasattr

&gt;&gt;&gt; for t in bpy.data.textures:
...     t.name, hasattr(t, "use_interpolation")
...     
('dice', True)
('Tex', True)
('Texture', False)


Find all with that property, then set.

bi_textures = [t for t in bpy.data.textures if hasattr(t, "use_interpolation")]
for t in bi_textures:
    t.use_interpolation = False


or get the textures from the materials on the planes. Test code to get all textures on selected nesh objects

import bpy

context = bpy.context

textures = [ts.texture 
        for o in context.selected_objects if o.type == 'MESH'
        for m in o.data.materials 
        for ts in m.texture_slots if ts and ts.texture]